Is there a term I can use for a boss's favorite employee?

Solution 1:

"Blue-eyed boy" is an idiomatic term used to describe "a person highly regarded by someone and treated with special favour".

... the problem that managers may favour their blue-eyed boys

2004, Jonathan Stroud, The Golem's Eye,

"Keep it up, Mandrake," he said. "Just keep it up. You may be the Prime Minister's blue-eyed boy now, but how long's that going to last if you don't deliver?"

Solution 2:

Neutral or positive connotations:
- star employee (this may be closest to "teacher's pet")
- protege (if the boss is nurturing the employee in some way)

Negative connotation:
- golden boy

Some of the terms suggested here (like "brown-noser") describe someone who is attempting to gain this status, but not all brown-nosers succeed. So a manager's favorite employee might or might not be a brown-noser, but being a brown-noser doesn't ensure that you're the favorite.

Solution 3:

Most terms for that relationship tend to have negative connotations. If it is a more positive relationship where the boss is mentoring your friend or grooming her for a better position, she would be his protégé.

Solution 4:

I'd actually use "teacher's pet" — use of metaphors is allowed in English.

Solution 5:

I think this person could describe themselves as the darling of the boss:

darling
O.E. deorling "darling, favorite minion"